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2 years ago

Calculate the percent activity of the radioactive isotope strontium-89 remaining after 5 half-lives.

1 answer:

5 0

The answer to this question would be: 3.125%

Half-life is the time needed for a radioactive molecule to decay half of its mass. In this case, the strontium-89 is already gone past 5 half lives. Then, the percentage of the mass left after 5 half-lives should be:
100%*(1/2^5)= 100%/32=3..125%

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For the following formula, C4H9Cl, calculate the IHD and select all the types of unsaturation that might be present in the molec

Airida [17]

Answer:

The IHD = 0

There is no unsaturation in the compound C4H9Cl

Explanation:

IHD = Index for Hydrogen Deficiency .It determines total number of unsaturation or Pi- bond present in the molecule.It is calculated using the formula:

For Molecule:

$C_{c}H_{h}O_{o}N_{n}X_{x}$

Here . C = carbon

H = Hydrogen

O = Oxygen

N = Nitrogen

X = Halogen

The IHD is calculated as :

$\frac{2c-h-x+n+2}{2}$ ...............(1)

For example :

C4H8O2

Here c = 4 , h = 8 , o = 2 .

n = x=0

Put the value in equation (1) and find IHD

$\frac{2(4)-8-0+0+2}{2}$

$\frac{8-8+2}{2}$

$\frac{2}{2}$

IHD = 1

For C4H9Cl

c = 4 , h = 9 and x = 1

IHD for this molecule can be calculated as :

$\frac{2c-h-x+n+2}{2}$

$\frac{2(4)-9-1+2}{2}$

$\frac{8-9-1+2}{2}$

= 0

This means there is no unsaturation in the molecule.

Each bond is sigma bond and properly saturated.

5 0

3 years ago

What is the molar mass of 37.96 g of gas exerting a pressure of 3.29 on the walls of a 4.60 L container at 375 K?

Phantasy [73]

The molar mass of the gas is 77.20 gm/mole.

Explanation:

The data given is:

P = 3.29 atm, V= 4.60 L T= 375 K mass of the gas = 37.96 grams

Using the ideal Gas Law will give the number of moles of the gas. The formula is

PV= nRT (where R = Universal Gas Constant 0.08206 L.atm/ K mole

Also number of moles is not given so applying the formula

n= mass ÷ molar mass of one mole of the gas.

n = m ÷ x ( x molar mass) ( m mass given)

Now putting the values in Ideal Gas Law equation

PV = m ÷ x RT

3.29 × 4.60 = 37.96/x × 0.08206 × 375

15.134 = 1168.1241 ÷ x

15.134x = 1168.1241

x = 1168.1241 ÷ 15.13

x = 77.20 gm/mol

If all the units in the formula are put will get cancel only grams/mole will be there. Molecular weight is given by gm/mole.

8 0

3 years ago

What is equal to the number of particles in 36 grams of carbon-12?

HACTEHA [7]

Answer:

3 moles

Explanation:

To solve this problem we will use the Avogadro numbers.

The number 6.022×10²³ is called Avogadro number and it is the number of atoms, ions or molecules in one mole of substance. According to this,

1.008 g of hydrogen = 1 mole = 6.022×10²³ atoms.

18 g water = 1 mole = 6.022×10²³ molecules

we are given 36 g of C-12. So,

12 g of C-12 = 1 mole

24 g of C-12 = 2 mole

36 g of C-12 = 3 mole

So 3 moles of C-12 equals to the number of particles in 36 g of C-12.

4 0

2 years ago

A 250.0-ml sample of ammonia, nh3 (g), exerts a pressure of 833 torr at 42.4 °c. what mass of ammonia is in the container

Lelu [443]

To solve this, let's assume ideal gas behavior.

PV=nRT
Let's solve for n. Convert units to SI units first.

Pressure = 833 torr(101325 Pa/760 torr) = 111,057.53 Pa
Volume = 250 mL(1 L/1000 mL)(1 m³/1000 L) = 2.5×10⁻⁴ m³
Temperature = 42.4 + 273 = 315.4 K

n = (8,314 J/mol·K)(315.4 K)/(111057.53 Pa)(2.5×10⁻⁴ m³)
n = 94.45 mol

The molar mass of ammonia is 17.031 g/mol.
Mass = 94.45*17.031 = <em>1,608.51 g ammonia</em>

6 0

3 years ago

How does changing temperature affect the solubility of gases in liquids?

Allisa [31]

Answer:

The solubility of gases in liquids decreases with increasing temperature. Conversely, adding heat to the solution provides thermal energy that overcomes the attractive forces between the gas and the solvent molecules, thereby decreasing the solubility of the gas; pushes the reaction in Equation 4 to the left

8 0

2 years ago